Troubleshooting; Auto-Restart Function - Carrier 38GRQB12-3 Service Manual

AUTO-RESTART FUNCTION

The indoor unit is equipped with auto-restart function, which is
carried out through an auto-restart module. In case of a sudden
power failure, the module memorizes the setting conditions present
previous to the power failure. The unit will automatically resume to
the previous operation settings (not including swing function) 3
minutes after the power returns.
If the memorization condition is forced cooling mode, the unit runs
in cooling mode for 30 minutes and returns to auto mode at a 75_F
(24_C) set temp. If the equipment was off before the power went
off, and it is required to start up after this power failure, the
compressor will have a 1 minute delay when powering on. In other
conditions, the compressor will have a 3 minutes delay at re-start.

TROUBLESHOOTING

This section provides the required flow charts to troubleshoot
problems that may arise.
NOTE: Information required in the diagnoses can be found
either on the wiring diagrams or in the appendix.
Required Tools:
The following tools are needed when diagnosing the units:
S Digital multimeter
S Screw drivers (Phillips and straight head)
S Needle- nose pliers
Recommended Steps
1 Refer to the diagnostic hierarchy charts below and
determine the problem at hand.
2 Go to the chart listed in the diagnostic hierarchy and follow
the steps in the chart for the selected problem.
For the ease of service, the systems are equipped with diagnostic
code display LED's on both the indoor and outdoor units. The
outdoor diagnostic display is on the outdoor unit board and is
limited to very few errors. The indoor diagnostic display is a
combination of flashing LED's on the display panel on the front
of the unit. If possible always check the diagnostic codes
displayed on the indoor unit first.
2.0
Problems may occur that are not covered by a diagnostic code, but
are covered by the diagnostic flow charts. These problems will be
typical air conditioning mechanical or electrical issues that can be
corrected using standard air conditioning repair techniques.
For problems requiring measurements at the control boards note
the following:
1 Always disconnect the main power.
2 When possible check the outdoor board first.
3 Start by removing the outdoor unit top cover.
4 Reconnect the main power
5 Probe the outdoor board inputs and outputs with a digital
multi- meter referring to the wiring diagrams.
6 Connect the red probe to hot signal and the black probe to
the ground or negative.
7 Note that some of the DC voltage signals are pulse will give
continuously variable readings.
8 If it is necessary to check the indoor unit board you must
start by disconnecting the main power.
9 Next remove the front cover of the unit and then control
box cover.
10 Carefully remove the indoor board from the control box,
place it face up on a plastic surface (not metal).
11 Reconnect the main power and repeat steps 5,6, and 7.
12 Disconnect main power before reinstalling board to avoid
shock hazard and board damage.
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